Apparatus and method for reconstructing ligaments

ABSTRACT

Apparatus for removing bone from a femoral notch, or the like, which includes a guidewire and a router assembly. The router assembly comprises a cutting head fixed to a shaft rotatably disposed in a hole through a body portion of a shield assembly. A hood portion of the shield assembly extends from the body portion of the shield assembly and covers a first portion of the cutting head while leaving exposed a second portion of the cutting head. The guidewire extends through a hole in the shaft, a hole in the cutting head, and a hole in the shield assembly hood portion, such that the router assembly is movable along the guidewire. The shaft is rotatable in the shield assembly body portion such that the second portion of the cutting head is engageable with the bone and operative to remove portions of the bone. The guidewire is installed in the knee so that it extends along the length to be occupied by a graft ligament. The guidewire and router assembly are flexible so that the bone-trimming operation may be conducted dynamically as the knee is moved through a range of natural motions.

This application is a continuation of application Ser. No. 09/083,889,filed May 22, 1998, now U.S. Pat. No. 5,941,883, which is a continuationof application Ser. No. 08/658,003, filed Jun. 4, 1996, now U.S. Pat.No. 5,755,718.

FIELD OF THE INVENTION

This invention relates to medical apparatus and methods in general, andmore particularly to apparatus and methods for reconstructing ligaments.

BACKGROUND OF THE INVENTION

Ligaments are tough bands of tissue which serve to connect the articularextremities of bones, or to support or retain organs in place within thebody. Ligaments are typically composed of coarse bundles of dense whitefibrous tissue which are disposed in a parallel or closely interlacedmanner, with the fibrous tissue being pliant and flexible, but notextensible.

In many cases, ligaments are torn or ruptured as a result of accidents.As a result, various procedures have been developed to repair or replacesuch damaged ligaments.

For example, in the human knee, the anterior and posterior cruciateligaments (i.e., the ACL and PCL) extend between the top end of thetibia and the bottom end of the femur. The ACL and PCL cooperate,together with other ligaments and soft tissue, to provide both staticand dynamic stability to the knee. Often, the anterior cruciate ligament(i.e., the ACL) is ruptured or torn as a result of, for example, asports-related injury. Consequently, various surgical procedures havebeen developed for reconstructing the ACL so as to restore normalfunction to the knee.

In many instances, the ACL may be reconstructed by replacing theruptured ACL with a synthetic or harvested graft ligament. Moreparticularly, with such procedures, bone tunnels are typically formed inthe top end of the tibia and the bottom end of the femur, with one endof the graft ligament being positioned in the femoral tunnel and theother end of the graft ligament being positioned in the tibial tunnel.The two ends of the graft ligament are anchored in place in various wayswell known in the art so that the graft ligament extends between thefemur and the tibia in substantially the same way, and withsubstantially the same function, as the original ACL. This graftligament then cooperates with the surrounding anatomical structures soas to restore normal function to the knee.

It will, of course, be appreciated that a complex interdependency existsbetween the ACL and the other elements of the knee, e.g., the bones, theother knee ligaments, and other soft tissue. Consequently, it iscritical that the graft ACL be disposed in exactly the right positionrelative to the other anatomical structures of the knee if normal kneefunction is to be restored. Correspondingly, it has been found that theaforementioned bone tunnels must be precisely positioned in the tibiaand femur if successful reconstruction of the ACL is to be achieved.Unfortunately, proper positioning of these bone tunnels to satisfyisometric considerations can sometimes lead to anatomical conflictswithin the knee when the graft ACL is installed within the knee.

More particularly, the ACL normally extends between the bottom end ofthe femur and the top end of the tibia, with the body of the ACL passingthrough the femur's intercondylar notch and across the interior of theknee joint. See, for example, FIGS. 1 and 2, which show a natural ACL 5extending between the bottom end of a femur 10 and the top end of atibia 15, with the body of ACL 5 passing through the femur'sintercondylar notch 20. Also shown is a natural PCL 25 extending betweenthe bottom end of femur 10 and the top end of tibia 15.

It is to be appreciated that the position of the various knee elementsmove relative to one another as the knee is flexed through a range ofnatural motions. See, for example, FIG. 3, which shows ACL 5 movingacross a 40° arc as the knee joint is flexed through a 140° motion.

Due to the complex geometries of the knee, where a damaged ACL is to bereplaced by a graft ACL, it is critical that the graft ACL be connectedat precisely the right locations on the bottom end of the femur and topend of the tibia. Thus, and looking now at FIGS. 4 and 5, where adamaged ACL is to be replaced by a graft ACL, the damaged ACL is firstcleared away and then bone tunnels 30 and 35 are formed in the tibia andfemur, respectively. The precise locations of these bone tunnels 30 and35 are dictated by the isometric relationships of the knee. In practice,bone tunnels 30 and 35 are formed using a surgical drill guide which iskeyed to certain parts of the patient's anatomy, e.g., to the patient'stibial plateau. Once bone tunnels 30 and 35 have been formed, the graftACL may be installed in ways well known in the art. See, for example,FIGS. 6 and 7, which show a graft ACL 5A having one end mounted to femur10 and the other end mounted to tibia 15.

Unfortunately, in some situations, proper isometric placement of bonetunnels 30 and 35 may cause anatomical conflicts within the knee whenthe graft ACL is installed in the patient. By way of example, and ofparticular interest in connection with the present invention, properisometric placement of bone tunnels 30 and 35 may result in portions ofthe femur impinging upon the graft ACL as the knee is moved through itsfull range of natural motions. See, for example, FIG. 8, which shows oneof the femur's condyles 40 impinging upon a graft ACL 5A extendingthrough the femur's intercondylar notch 20; and FIG. 9, which shows theroof the femur's intercondylar notch impinging on the graft ACL 5A inthe vicinity of arrow 42.

Impingement can occur for a variety of reasons. For one thing, theintercondylar notch of many patients (particularly those who aresusceptible to rupture of the ACL) is frequently small to begin with.For another thing, the graft ACL (i.e., the synthetic or harvested graftligament which is being installed in place of the damaged natural ACL)is generally fairly large.

Additionally, slight mispositioning of bone tunnels 30 and 35 can alsolead to impingement problems.

Unfortunately, impingement of the femur on the graft ligament can reducethe effectiveness of the ACL reconstruction procedure or even cause itto fail altogether.

Thus, when performing an ACL reconstruction procedure, the surgeongenerally tries to ensure that there is sufficient room within thepatient's intercondylar notch to receive the graft ligament. This isgenerally done by performing notchplasty, i.e., by surgically removingany impinging bone from the sides and/or roof of the intercondylarnotch. At the same time, of course, it is also important that thesurgeon remove no more bone than is absolutely necessary, so as tominimize trauma to the patient.

Unfortunately, it is difficult for the surgeon to accurately gauge theprecise amount of bone that must be removed from the notch in order toavoid impingement. For one thing, the ACL reconstruction procedure istypically performed arthroscopically, so that the surgeon's view of thesurgical site is frequently fairly restricted. For another thing, thesurgeon typically will not know the precise space that the graft ACLwill occupy until the graft is actually in place; but at that point inthe procedure, it is frequently difficult to insert additionalbone-cutting instruments into the joint so as to remove more bone,particularly without cutting the graft ACL. Furthermore, experience hasshown that the most serious problems with impingement occur superiorly;but even with the graft ligament in place, the surgeon is generallyunable to see impingement at this location due to limitations inarthroscopic visualization. Also, the surgeon typically performs the ACLreconstruction procedure in a relatively static context, i.e., with theknee being relatively stationary at any given moment during thereconstruction procedure. However, the knee must perform (andimpingement must be avoided) in a relatively dynamic context, i.e., asthe knee is moved throughout a full range of natural motions. Thiscomplicates the surgeon's task of eliminating impingement.

Objects Of The Invention

Accordingly, one object of the present invention is to provide improvedapparatus for reconstructing a ligament.

Another object of the present invention is to provide improved apparatusfor reconstructing an anterior cruciate ligament (ACL).

And another object of the present invention is to provide improvedapparatus for quickly, easily and reliably eliminating impingementproblems when reconstructing an anterior cruciate ligament.

Still another object of the present invention is to provide improvedapparatus for quickly, easily and reliably removing any anatomicalstructures (e.g., bone) which will conflict with the location of a graftACL at the completion of an ACL reconstruction procedure.

Yet another object of the present invention is to provide improvedapparatus for quickly, easily and reliably removing any anatomicalstructures (e.g., bone) which will conflict with the location of a graftACL as the knee is moved through a full range of natural motions.

And an object of the present invention is to provide an improved methodfor reconstructing a ligament.

Another object of the present invention is to provide an improved methodfor reconstructing an anterior cruciate ligament (ACL).

And another object of the present invention is to provide an improvedmethod for quickly, easily and reliably eliminating impingement problemswhen reconstructing an anterior cruciate ligament.

Still another object of the present invention is to provide an improvedmethod for quickly, easily and reliably removing any anatomicalstructures (e.g., bone) which will conflict with the location of a graftACL at the completion of an ACL reconstruction procedure.

Yet another object of the present invention is to provide an improvedmethod for quickly, easily and reliably removing any anatomicalstructures (e.g., bone) which will conflict with the location of a graftACL as the knee is moved through a full range of natural motions.

SUMMARY OF THE INVENTION

These and other objects are addressed by the present invention, whichcomprises the provision and use of novel apparatus for removingimpinging bone during a ligament reconstruction procedure.

In one preferred form of the invention, the novel apparatus comprises aguidewire and a router assembly.

The guidewire is similar to other guidewires of the sort well known inthe art, except that it is preferably formed out of a pseudoelasticmaterial, i.e., a “shape memory alloy (SMA)/stress induced martensite(SIM)” material such as Nitinol.

The router assembly comprises a cannulated router device and a shieldassembly. The cannulated router device comprises a cannulated cuttinghead which is attached to a cannulated shaft. The shield assemblycomprises a body and a hood. The body includes a hole therein. The hoodextends about one end of the body. The router assembly is assembled sothat the router device has its cutting head disposed at one end of theshield assembly's body and the router device has its shaft extendingthrough the hole in the shield assembly's body. The shield assembly'shood covers a first portion of the router device's cutting head whileleaving a second portion of the cutting head exposed.

The guidewire is deployed in the body so that it extends along thelength where the graft ACL will reside. The router assembly is mountedon the guidewire by passing the guidewire through the router device'sshaft and cutting head, such that the router assembly is movable alongthe guidewire. The router device's shaft is rotatable in the shieldassembly such that the cutting head can be turned so as to remove bonewhile the router assembly is riding on the guidewire. Portions of therouter assembly engaging the guidewire are formed so as to be flexible.On account of the fact that both the guidewire and portions of therouter assembly are formed so as to be flexible, the router assembly canbe used to remove impinging bone as the knee is flexed through a fullrange of natural motions.

In accordance with another form of the invention, there is providedalternative apparatus for removing impinging bone, the alternativeapparatus comprising a guidewire and a cannulated router device. Again,the guidewire is preferably formed out of a pseudoelastic material. Thecannulated router device comprises a cannulated cutting head which isattached to a cannulated shaft. In this embodiment of the invention, thecutting head is devoid of cutting means on a first portion of theperiphery thereof and is provided with cutting means on a second portionof the periphery thereof. The second portion of the cutting head isengageable with the impinging bone portions which are to be removed.

Again, the guidewire is deployed in the body so that it extends alongthe length where the graft ACL will reside. The router device is mountedon the guidewire by passing the guidewire through the router device'sshaft and cutting head, such that the router device is movable on theguidewire. The router device is rotatably movable in an oscillatingfashion such that the cutting head's second portion moves in alternatingopposite directions across the impinging bone to remove portionsthereof. The first portion of the cutting head is smooth andnon-destructive with respect to any anatomical structures which thefirst portion may come into contact with. Portions of the router deviceengaging the guidewire are formed so as to be flexible. On account ofthe fact that both the guidewire and portions of the router device areformed so as to be flexible, the router device can be used to removeimpinging bone as the knee is flexed through a full range of naturalmotions.

In accordance with another form of the invention, there is providedalternative apparatus for removing impinging bone, the alternativeapparatus comprising a guidewire and a cannulated router device. Again,the guidewire is preferably formed out of a pseudoelastic material. Thecannulated router device comprises a cannulated cutting head which isattached to a cannulated shaft. In this embodiment of the invention, thecutting head is adapted to cut bone which comes into contact with thecutting head, but to leave unharmed soft tissue which comes into contactwith the cutting head.

Again, the guidewire is deployed in the body so that it extends alongthe length where the ACL graft will reside. The router device is mountedon the guidewire by passing the guidewire through the router device'sshaft and cutting head, such that the router device is movable on theguidewire. The router device is rotatably movable on the guidewire so asto cut away impinging bone. Again, portions of the router deviceengaging the guidewire are formed so as to be flexible. On account ofthe fact that both the guidewire and portions of the router device areformed so as to be flexible, the router device can be used to removeimpinging bone as the knee is flexed through a full range of naturalmotions.

In accordance with another form of the invention, there is providedapparatus for marking portions of impinging bone which are to bethereafter removed, the apparatus comprising a guidewire and acannulated marking device. Again, the guidewire is preferably formed outof a pseudoelastic material. The cannulated marking device comprises acannulated marker head attached to a cannulated shaft.

Again, the guidewire is deployed in the body so that it extends alongthe length where the graft ACL will reside. The marking device ismounted on the guidewire by passing the guidewire through the markingdevice's shaft and marking head, such that the marking head is movableon the guidewire. The marking head is adapted to hold a dye and torelease that dye upon contact with bone, whereby to mark the impingingportions of the bone proximate to the guidewire as the marking headmoves on the guidewire. Portions of the marking device engaging theguidewire are formed so as to be flexible. On account of the fact thatboth the guidewire and portions of the marking device are formed so asto be flexible, the marking device can be used to mark impinging bone asthe knee is flexed through a full range of natural motions.

In accordance with a further feature of the invention, there is provideda method for removing impinging portions of bone, the method comprisingthe steps of providing a flexible guidewire and a flexible cannulatedrouter device. The guidewire is anchored in the bone so that it extendsalong the length where the graft ACL will reside, and the cannulatedrouter device is rotatably mounted on the guidewire so that it ismovable on the guidewire. Then the cannulated router device is rotatedon the guidewire as the knee is flexed through a range of naturalmotions so as to dynamically remove impinging bone.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects and features of the present invention will bemore fully disclosed or rendered obvious by the following detaileddescription of the preferred embodiments of the invention, which are tobe considered together with the accompanying drawings wherein likenumbers refer to like parts and further wherein:

FIG. 1 is a schematic front view of a normal knee, where the leg issubstantially straight;

FIG. 2 is a schematic side view, partially in section, of the knee shownin FIG. 1;

FIG. 3 is a schematic side view, showing how the ACL moves about withinthe knee joint as the knee is flexed through a range of natural motions;

FIG. 4 is a schematic front view of a knee, where the knee is bent atapproximately a 90° angle, and where a damaged ACL has been removed andbone tunnels have been formed in the tibia and the femur;

FIG. 5 is a schematic side view of the knee shown in FIG. 4;

FIG. 6 is a schematic front view of a knee, where the knee is bent atapproximately a 90° angle, showing a graft ACL installed in the knee;

FIG. 7 is a schematic side view of the knee shown is FIG. 6;

FIG. 8 is a schematic front view showing how portions of the femur canimpinge upon a graft ACL;

FIG. 9 is a schematic side view showing how portions of the femur canimpinge upon a graft ACL;

FIG. 10 is a schematic side view of the guidewire used in connectionwith the present invention;

FIG. 11 is a schematic perspective view showing one form of routerassembly formed in accordance with the present invention;

FIG. 12 is a schematic perspective view of the router assembly'scannulated router device;

FIG. 13 is a schematic side view, in section, of the cannulated routerdevice shown in FIG. 12;

FIG. 14 is a schematic side view, in section, of a portion of the routerassembly's shield assembly;

FIG. 15 is a schematic perspective view of the shield assembly's collar;

FIG. 16 is a schematic side view, in section, of the router assemblyshown in FIG. 11;

FIG. 17 is a schematic side view of a knee, where the knee is bent atapproximately a 90° angle, and where a damaged ACL has been removed anda bone tunnel has been formed in the tibia, and showing a guidewireextending through the tibial bone tunnel and into the femur;

FIG. 18 is a schematic side view of the knee shown in FIG. 17;

FIG. 19 is a schematic front view like that of FIG. 17, except showing arouter assembly removing lateral bone structures from the femoral notchso as to prevent those lateral bone structures from impinging on a graftACL;

FIG. 20 is a schematic side view showing a router assembly removinglateral bone structures from the femoral notch so as to prevent thoselateral bone structures from impinging on a graft ACL;

FIG. 21 is a schematic front view, showing the leg substantiallystraight and the router assembly removing roof bone structures from thefemoral notch so as to prevent those roof bone structures from impingingon a graft ACL;

FIG. 22 is a schematic side view of the knee and router assembly shownin FIG. 21;

FIG. 23 is a schematic side view, showing the knee flexed atapproximately a 140° angle and the router assembly removing bonestructures from the femoral notch so as to prevent those bone structuresfrom impinging on a graft ACL;

FIG. 24 is a schematic perspective view showing an alternative form ofrouter assembly formed in accordance with the present invention;

FIG. 25 is a schematic perspective view showing the collar used inconnection with the router assembly shown in FIG. 24;

FIG. 26 is a schematic side view, in section, of the router assemblyshown in FIG. 24;

FIG. 27 is a schematic perspective view of another form of router devicewhich can be used in connection with the present invention;

FIG. 28 is a schematic perspective view of yet another form of routerdevice which can used in connection with the present invention;

FIG. 29 is a schematic side view of a cannulated marking device formedin accordance with the present invention; and

FIG. 30 is a schematic side view of a novel type of guidewire assemblyformed in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Looking first at FIGS. 10-16, the present invention provides apparatusand a method for removing bone structures from the femoral notch so asto prevent those bone structures from impinging upon a graft ACLinstalled as part of an ACL reconstruction procedure. The apparatus andmethod of the present invention are intended to be utilized in an ACLreconstruction procedure after the damaged ACL has been removed from theknee and after bone tunnel 30 has been formed in tibia 15, but beforebone tunnel 35 has been formed in femur 10 and the graft ACL has beenpositioned in the joint.

Still looking now at FIGS. 10-16, in one preferred embodiment of thepresent invention, the apparatus of the present invention comprises aguidewire 50 (FIGS. 10 and 11) and a router assembly 55 (FIGS. 11-16).

Guidewire 50 is generally of the sort well known in the art for guidingcannulated elements to a target structure. As such, guidewire 50includes a sharp point 60 (FIG. 10) on its distal end, whereby theguidewire can be drilled or tapped into a target structure (e.g., femur10, as will hereinafter be described in further detail). However, unlikeother guidewires of the sort known in the art, and in accordance withone preferred embodiment of the present invention, guidewire 50 ispreferably formed out of a highly elastic yet firm material. Preferably,guidewire 50 is formed out of a so-called pseudoelastic material, i.e.,a “shape memory alloy (SMA)/stress induced martensite (SIM)” materialsuch as Nitinol. By forming guidewire 50 out of such a highly elasticyet firm material, the guidewire has the rigidity needed to penetrateinto bone, yet has the high elasticity needed to undergo substantialelastic deformation during joint flexure, as will hereinafter bedescribed in further detail.

Still looking now at FIGS. 11-16, router assembly 55 comprises acannulated router device 65 (FIGS. 11-13 and 16) which comprises acannulated cutting head 67 attached to a cannulated shaft 70. At leastthe distal portion 70′ (FIGS. 12, 13 and 16) of cannulated shaft 70 isflexible; the proximal portion 70″ of cannulated shaft 70 may or may notbe flexible, as desired. On account of this construction, cannulatedrouter device 65 can ride on guidewire 50 as rotary cutting motion isimparted to cutting head 67 by means of shaft 70. In particular, byforming at least the distal portion 70′ of cannulated shaft 70 so as tobe flexible, router device 65 can ride on guidewire 50 and rotate evenas guidewire 50 is subjected to substantial bending during knee jointflexure, as will hereinafter be discussed in further detail.

Router assembly 55 also comprises a shield assembly 75 (FIGS. 11 and14-16). Shield assembly 75 comprises a body assembly 80 and a hood 85.

Body assembly 80 comprises a hollow outer tube 82 (FIGS. 14 and 16) andan inner collar 83 (FIGS. 15 and 16). At least the distal portion 82′(FIGS. 14 and 16) of hollow outer tube 82 is flexible; the proximalportion 82″ of hollow outer tube 82 may or may not be flexible, asdesired. Collar 83 is sized and positioned so as to terminate at thejuncture of the hollow tube's distal portion 82′ and its proximalportion 82″ (FIG. 16). Collar 83 includes a hole 90 (FIGS. 15 and 16)for receiving shaft 70 of router device 65. Hole 90 is preferablycentered within body 80, whereby the router device's cutting head 67will be centered within shield assembly 75.

Hood 85 is attached to body 80 and includes a hole 95 (FIGS. 14 and 16)for receiving guidewire 50. Hood 85 surrounds a portion of the routerdevice's cutting head 67 but leaves another portion of the cutting head(i.e., the portion extending outboard of hood 85) exposed for routingoperations. By way of example but not limitation, hood 85 might coverapproximately ⅔ of the circumferential region surrounding cutting head67 and leave approximately ⅓ of the circumferential region surroundingcutting head 67 exposed for cutting purposes. Shield 85 may be formedflexible or rigid, as desired.

As a result of this construction, router assembly 55 can ride onguidewire 50 as a unit, with shaft 70 rotating cutting head 67 so as tocut away any material (e.g., impinging bone) exposed to the cuttinghead, even as hood 85 shields a substantial portion of the cutting headfrom inadvertently cutting other material (e.g., the patient's PCL).Significantly, due to the flexible nature of shaft portion 70′ and tubeportion 82′, router assembly 55 is able to ride on guidewire 50 even asguidewire 50 is subjected to substantial deformation during knee jointflexure.

Looking next at FIGS. 17-23, guidewire 50 and router assembly 55 areintended to be used as follows.

First, femur 10 and tibia 15 are set at approximately a 90° angle andtibial bone tunnel 30 is formed in tibia 15. Then guidewire 50 is passedthrough tibial bone tunnel 30 and into femur 10 until the sharp distalend 60 of the guidewire is embedded in the femur, e.g., by drilling ortapping in ways well known in the art (see FIGS. 17 and 18). If desired,a cannulated guide of the sort well known in the art (not shown) may bedisposed about guidewire 50 to help stabilize it as it is embedded intofemur 10. Guidewire 50 is positioned in the patient so that it willextend along the length where the graft ACL will reside.

Next, router assembly 55 is loaded onto the proximal end of guidewire 50and moved down into the interior of the knee joint so that the routerassembly's cutting head 67 is in the vicinity of femoral notch 20 (seeFIGS. 19 and 20). Then body 80 of router assembly 55 is turned so thatthe router assembly's cutting head 67 is directed toward the impingingportions of the femur which are to be removed, and so that the routerassembly's protective hood 85 is placed between the cutting head and thePCL so as to protect the PCL from the cutting head. Then shaft 70 isrotated, e.g., with a power driver (not shown) of the sort well known inthe art, so as to rotate cutting head 67 and thereby cut away anyanatomical structures it comes into contact with.

By turning body 80 circumferentially as required, cutting head 67 can beused to enlarge femoral notch 20 while keeping the cutting head fromengaging (and thereby cutting) the PCL and/or other sensitive anatomicalstructures. In particular, by turning router assembly 55 so that itfaces in the manner shown in FIGS. 19 and 20, lateral notch structurescan be removed. Similarly, by turning router assembly 55 so that itfaces in the manner shown in FIGS. 21 and 22, roof notch structures canbe removed.

Significantly, the impinging bone can be removed quickly, easily andsafely, without direct visualization of the anatomical structures beingtrimmed away, due to the use of guidewire 50 and the guidewire-followingrouter assembly 55.

In particular, it is to be appreciated that, by positioning guidewire 50so that it will extend along the length where the graft ACL will reside,and by properly sizing the radial dimensions of router assembly 55relative to the graft ACL which will thereafter be installed, the routerassembly will clear away only as much bone as is required to properlysize the femoral notch and eliminate impingement problems. Furthermore,by properly sizing the longitudinal dimensions of router assembly 55relative to the notch region where impingement occurs, impingement canbe eliminated by just circumferential movement of router assembly 55 onguidewire 50, i.e., without requiring longitudinal movement of routerassembly 55 on guidewire 50 during bone-trimming operations.

Significantly, since guidewire 50 is preferably formed out of a highlyelastic material, and since the router assembly's shaft portion 70′ andbody portion 82′ are formed so as to be flexible, it is possible to userouter assembly 55 to remove impinging bone in a dynamic sense, i.e., touse the router assembly to cut away impinging bone even as the knee isflexed through a full range of natural motions. See, for example, FIGS.19 and 20, where router assembly 55 is shown enlarging the femoral notchwhile the patient's leg is bent at approximately a 90° angle; FIGS. 21and 22, where router assembly 55 is shown enlarging the femoral notchwhile the patient's knee is substantially straight; and FIG. 23, whererouter assembly 55 is shown enlarging the femoral notch while thepatient's knee is bent at approximately a 140° angle. It should be notedin FIGS. 21 and 22, and again in FIG. 23, how guidewire 50 and routerassembly 55 are capable of undergoing substantial elastic deformationduring such knee flexing even as bone-trimming operations are under way.

Looking next at FIGS. 24-26, in another preferred embodiment of thepresent invention, the apparatus of the present invention comprisesguidewire 50 and a router assembly 55A.

Router assembly 55A is substantially the same as router assembly 55described above, except as is shown in the drawings and/or hereinafterdescribed. In particular, router assembly 55A utilizes a collar 83A(FIGS. 25 and 26) rather than the collar 83 described above. Collar 83Ahas its hole 90 disposed off-center within the collar, whereby therouter device's cutting head 67 will be clocked to one side relative tothe body's hollow outer tube 82 (see FIG. 26). In particular, withrouter assembly 55A, collar 83A is arranged so that the router device'scutting head 67 is clocked outboard relative to the central axis ofhollow outer tube 82. This permits the router device to engage impingingbone more readily. In order to accommodate such lateral displacement ofrouter device 65, the router assembly's shield 85A has its hole 95Ashifted laterally as well, in the manner shown in FIG. 26.

In operation, router assembly 55A is intended to be used insubstantially the same way as router assembly 55.

Looking next at FIG. 27, in another preferred embodiment of the presentinvention, the apparatus of the present invention comprises guidewire 50and a cannulated router device 65A. Router device 65A is generallysimilar to the router device 65 discussed above, except that with routerdevice 65A, its cutting teeth 89 are disposed about only a portion ofthe periphery of its cutting head 67A, with the remainder of the cuttinghead being smooth and non-abrasive. Accordingly, by moving cannulatedrouter device 65A on guidewire 50 so as to oscillate the router devicethrough only a fraction of a complete revolution, bone can be removedadjacent to the cutting teeth 89 while the remainder (i.e., thenon-cutting portion) of the cutting head 67A safely opposes any delicatestructures which are to be safeguarded (e.g., the PCL). Thus, with theapparatus of FIG. 27, impinging bone may be safely removed withoutproviding a shield assembly (e.g., such as the shield assembly 75described above) for the router device.

In another form of the invention, the cannulated router device 65A ofFIG. 27 could be replaced with a cannulated router device of the sortadapted to remove hard bone while leaving soft tissue unharmed. By wayof example, the cannulated router device 65A of FIG. 27 might bereplaced by the cannulated router device 65B shown in FIG. 28. Moreparticularly, router device 65B includes a cutting head 67B having anouter configuration similar to that disclosed in U.S. Pat. No. 4,445,509issued May 1, 1984 to David C. Auth for METHOD AND APPARATUS FOR REMOVALOF ENCLOSED ABNORMAL DEPOSITS, which patent is hereby specificallyincorporated herein by reference. Alternatively, cutting head 67B couldhave some other configuration of the sort well known in the art whichpermits cutting of hard bone without harming soft tissue. As a result ofsuch a construction, a cannulated router device 65B having such aconfiguration could then be safely rotated completely about guidewire 50so as to remove impinging bone without risking damage to delicate softtissue. Thus, with the apparatus of FIG. 28 or with equivalent cuttingapparatus, impinging bone can be safely removed without providing ashield assembly (such as the shield assembly 75 described above) for therouter device.

The foregoing apparatus may be used in an ACL reconstruction procedureas follows. First, the patient's knee is extended at an angle ofapproximately 90°. Then, a bone tunnel 30 is formed in the tibia in wayswell known in the art. Next, guidewire 50 is passed through bone tunnel30 and up into the femur. Then a cannulated router device (in the formof either router assembly 55, or router assembly 55A, or router device65A, or router device 65B) is loaded onto guidewire 50 and used toperform the desired notchplasty in the manner previously described.Next, the cannulated router device is dismounted from guidewire 50. Thenbone tunnel 35 is formed in femur 10 in ways well known in the art. Thenguidewire 50 is removed from femur 10. Finally, a graft ACL 5A isinstalled in femoral bone tunnel 35 and tibial bone tunnel 30 in wayswell known in the art.

Looking next at FIG. 29, in another preferred embodiment of the presentinvention, the apparatus of the present invention comprises guidewire 50and a marking device 100. Marking device 100 preferably comprises aresilient cannulated head 105 and a flexible cannulated shaft 110connected to head 105. Cannulated head 105 is formed so that it can holdand release a dye without cutting bone. Marking device 100 is used bymoving the device up and down guidewire 50, with or without rotation,whereby the marking head 105 will contact any bone in its way. By sizingmarking device 100 properly relative to the size of the graft ACL whichis to be installed, movement of marking device 100 along guidewire 50while the knee is moved through a range of natural motions will causethe marking element to leave its dye on any portions of the femur whichmight impinge upon the graft ACL which will thereafter be installed inthe knee. Thereafter, marking device 100 and guidewire 50 are removedfrom the surgical site and the surgeon may utilize a conventionalcutting element to remove the marked bone. Then the graft ACL may beinstalled in the knee without fear of impingement.

In the foregoing description of the preferred embodiments of theinvention, it was noted that guidewire 50 is preferably formed out of apseudoelastic material so as to provide the desired characteristics offirmness and flexibility. However, it should also be appreciated that aguidewire made out of a non-pseudoelastic material can also be utilizedin connection with the present invention. Of course, inasmuch as thepreferred use of the present invention involves flexing the knee over awide range of motions with the guidewire in place, limitations in wireflexibility can inhibit the range of knee movements performed with theguidewire in place. Thus, in the situation where a non-pseudoelasticguidewire is to be used, it can be helpful to mount the distal end ofthe guidewire in a fixture by means of a universal joint. This fixturecan then be attached to the bottom surface of the femur or, moreadvantageously, it can be disposed in a bore formed in the bottom of thefemur. Preferably this bore is the femoral bone tunnel 35 used for theACL reconstruction procedure.

More particularly, and looking now at FIG. 30, the distal end of anon-pseudoelastic guidewire 50A can be mounted in a fixture 115 by auniversal joint 120 whereby the proximal end of the guidewire can moveabout relative to fixture 115. As a result of this construction, whenfixture 115 is positioned in the femoral bone tunnel, universal joint120 will help guidewire 50A to accommodate the degree of deformationrequired as the knee is moved through a full range of natural motions.Of course, with this embodiment of the invention, the femoral bonetunnel 35 must be formed before the notchplasty procedure is performed,since fixture 115 is intended to be received in bone tunnel 35.

Modifications of the Preferred Embodiments

It is to be appreciated that modifications may be made to the preferredembodiments described and illustrated above without departing from thescope of the present invention

Thus, for example, while in the foregoing description the presentinvention has been described in the context of reconstructing an ACL, itshould also be appreciated that the present invention has application tothe reconstruction of other ligaments as well, where similar impingementproblems can occur. Thus, for example, the present invention might beused in connection with reconstructing the posterior cruciate ligament(PCL).

The present invention can also be used to clear away impingingstructures in other anatomical and non-anatomical settings.

Advantages of the Invention

Numerous advantages are achieved through the use of the presentinvention.

For one thing, the present invention provides improved apparatus forreconstructing a ligament.

And the present invention provides improved apparatus for reconstructingan anterior cruciate ligament (ACL).

Also, the present invention provides improved apparatus for quickly,easily and reliably eliminating impingement problems when reconstructingan anterior cruciate ligament.

And the present invention provides improved apparatus for quickly,easily and reliably removing any anatomical structures (e.g., bone)which will conflict with the location of a graft ACL at the completionof an ACL reconstruction procedure.

The present invention also provides improved apparatus for quickly,easily and reliably removing any anatomical structures (e.g., bone)which will conflict with the location of a graft ACL as the knee ismoved through a full range of natural motions.

The present invention also provides an improved method forreconstructing a ligament.

And the present invention provides an improved method for reconstructingan anterior cruciate ligament (ACL).

And the present invention provides an improved method for quickly,easily and reliably eliminating impingement problems when reconstructingan anterior cruciate ligament.

Also, the present invention provides an improved method for quickly,easily and reliably removing any anatomical structures (e.g., bone)which will conflict with the location of a graft ACL at the completionof an ACL reconstruction procedure.

And the present invention provides an improved method for quickly,easily and reliably removing any anatomical structures (e.g. bone) whichwill conflict with the location of a graft ACL as the knee is movedthrough a full range of natural motions.

What is claimed is:
 1. Apparatus for removing portions of a bone formingpart of a joint, said apparatus comprising: a router assemblycomprising: a cutting head fixed to a shaft; and a shield assemblyhaving a body portion and a hood portion, said body portion having ahole therethrough for receiving said shaft, said hood portion extendingfrom one end of said body portion and defining a concavity in which isdisposable in part said cutting head, wherein said cutting head and saidshaft are provided with bores in alignment with each other and adaptedto receive a guidewire therethrough, and further wherein said hoodportion is provided with a hole therein alignable with said cutting headbore and adapted to receive said guidewire; and the guidewire, saidguidewire extending through said shaft, said cutting head and saidshield hood portion hole, said shaft, said cutting head, and said shieldassembly being movable along said guidewire to advance said routerassembly along said guidewire; said shaft, said shield assembly and saidguidewire being flexible, and said distal end of said guidewire beingadapted for positioning in a bone, whereby when said distal end of saidguidewire is positioned in a bone, the router assembly may thereafter bemoved along said guidewire while said joint is flexed and said guidewireis bent so as to permit the cutting head to remove any intervening bone.2. Apparatus according to claim 1 wherein said body portion iscylindrically shaped and said body portion hole extends lengthwise ofsaid cylindrically shaped body portion and the central axis of said bodyportion hole is removed from a central axis of said body portion. 3.Apparatus according to claim 2 wherein said shield portion encloses afirst portion of said cutting head, and a second portion of said cuttinghead extends outwardly from said shield portion.
 4. Apparatus accordingto claim 3 wherein a portion of the perimeter of said second portion ofsaid cutting head is substantially aligned with a portion of theperimeter of said body portion.
 5. Apparatus according to claim 3wherein said first portion of said cutting head includes a majority ofthe circumference of said cutting head.
 6. Apparatus according to claim3 wherein said shield assembly body portion comprises a collar within asleeve, said body portion hole extending through said collar. 7.Apparatus according to claim 1 wherein said apparatus further comprises:the guidewire, said guidewire being formed out of a pseudoelasticmaterial.